Y position always on top of an object!

Question

Riiiight heyyyyy, my new question is... how do you make the y
position of an object always be just above another object, e.g. on
most games on the internet an object or "player" can move over
other objects like "ground" and obstacles, in my quite simple game,
I've been trying to get the ball to roll over a simple "floor" Mc
using hitTest using
_y -- or _y -= 1 to get the object to stay over the floor,
this works fine on horizontal "floor" but on parts where the floor
raises it moves straight through it and goes up slowly if the ball
remains inside the Mc until it reaches the top of it,
Is there a way to keep the ball constantly 1px above the Mc?
Thaaaaaaaanks in advanceeee!

Answer 1

there's no easy fix. you'll need to code for that.
if you have a simple shaped ground, just code directly.
if you have a complex irregularly shaped ground, you can use
the bitmapdata class to record the "height" of your ground as a
function of _x and in your loop that's used to change the ball's _x
property, check the corresponding "height" of the ground and adjust
your ball accordingly.